For the moment, we can transfer pictures between instances in the CLI, but IDs are lost (linked to #314). It might be handy to implement pictures transfers directly in the backend, as an async job to transfer owned pictures from an instance to a new instance. It should be configured in the target instance I think, and using some mean to authenticate on the first instance to make sure the pictures are owned by the user. Using a token for this should be the easiest way to handle this. Compared to doing this with the CLI, it will reduce the bandwidth used (since with the CLI, we need to download the pictures before uploading them) and it will be possible to have a nice page on the website to automate account transfers when new instances are installed.